“Over the last few days, the ship began seeing an increased number of gastrointestinal illnesses, caused by norovirus (commonly referred to as the stomach flu),” said Princess Cruises spokeswoman Susan Lomax, via email. “In response, we have enacted our stringent disinfecting protocols developed in conjunction with the U.S. Centers for Disease Control (CDC), which includes an extensive deep cleaning of the ship and the terminal in Los Angeles on Sunday before the ship embarks on its next voyage.”

The CDC statement confirmed the ship has implemented CDC sanitation procedures to slow the disease’s spread. The cruise line also made announcements to notify onboard passengers of the outbreak, encouraging hand hygiene and case reporting. Passengers about to board the ship were also supposed to be notified.

At least 122 of 3,161 passengers and 30 of 1,176 crew members aboard the Crown Princess were sickened on an April sailing, according to the CDC. The federal agency blamed norovirus and E. Coli for the outbreak.

Norovirus is known for being quite contagious. It causes nausea, vomiting and diarrhea and is believed to have infected passengers on a number of cruise ships this year.

“As it is the cold and flu season, when the stomach flu circulates on land, we encourage all of our guests to be diligent in following the widely accepted practices of frequent hand washing with soap and water and the use of hand sanitizers,” said Lomax.

In February, 114 passengers and 10 crew members took ill on the Holland America cruise ship MS Veendam during a weeklong voyage.

In January, more than 600 people on cruise ships sailing in the Caribbean fell ill from the virus, the CDC reported.

Norovirus infects many people on land, but health officials track it on cruise ships, leading to more frequent reporting of cases, the CDC said.

It is passed in person-to-person contact and can spread more easily in closed quarters.